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Body systems- respiratory > Development of the respiratory system > Flashcards

Development of the respiratory system Flashcards

1
Q

What is the URT (conducting portion) made up of?

A
  • Nasal cavities
  • Nasopharynx
  • Oropharynx
  • Larynx
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2
Q

What is the LRT (conducting portion) made up of?

A
  • Trachea
  • Bronchi
  • Bronchioles
  • Terminal bronchioles
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3
Q

What is the LRT (respiratory portion) made up of?

A
  • Respiratory bronchioles
  • Alveolar ducts
  • Alveolar sacs
  • Alveoli
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4
Q

What is the point of transition from upper to lower RT?

A

Larynx

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5
Q

Where does the inner epithelial lining of the trachea/ bronchi come from?

A

Inner epithelial lining of the trachea/ brochi comes from the endoderm.

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6
Q

Where does the connective tissue and C shaped cartilage come from?

A

C shaped cartilage rings and connective tissues come from the mesoderm.

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7
Q

At week 4 what does the embryo look like?

A

Yolk sac visible, somites visible, CNS development, gut tube (foregut, midgut, hindgut). Respiratory diverticulum (lung bud) appears in ventral wall of foregut. Derived from endoderm.

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8
Q

How is the gut tube divided?

A

Gut tube- split into foregut- goes from oropharyngeal membrane to septum transversum, midgut- yolk sac and the vitelline duct, hind gut- anything distal to the yolk sac.
Foregut- in it we have a R diverticulum (a growth)- gut tube where we develop out R system/ tract

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9
Q

How does the lung bud from and at what day does it appear?

A
  • Appears day 22
  • Grows ventrocaudally
  • Tracheoesophagul ridges separate the respiratory diverticulum from the foregut (except laryngeal inlet)
  • Dorsally oesophagus
  • Ventrally trachea and lung bud which has now divided to form two lung buds
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10
Q

What is a fistula?

A

An abnormal connection

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11
Q

What is a tracheoesophageal fistulas?

A

A fistula is an abnormal communication and results from incomplete division of the foregut into oesophagul and respiratory portions.

Abnormal connections between trachea and oesophagus

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12
Q

What is atresia?

A

When oesophagus ends up a blind ended sac

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13
Q

Tracheoesophageal fistula with oesphageal astresia- what is it?

A

distal part of oesphagus still connected to trachea-proximally oesphagus is a blind ended sac- narrowed so much it closes- oesophagus atresia

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14
Q

What is an H type tracheoesophagul fistula?

A

Fistula between trachea and oesophagus

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15
Q

What happens when tracheoesophageal fistula with oesphageal astresia occurs?

A
  • Upper oesophagus ends abruptly; lower oesophagus forms fistula with trachea
  • Abdomen rapidly distends as stomach fills with air- inspired air down trachea then down each of bronchi- abnormal connection between trachea and oesophagus- air can escape into oesophagus- into the stomach
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16
Q

What congenital abnormalities are tracheoesophageal fistulas associated with?

A

Component of either the Vacterl or Vater associated abnormalities:

V vertebral defects
A Anal atresia
(C) Cardiac defects
T Tracheo-oesophageal fistulas
E Esophageal atresia 
R Renal abnormalities
(L) Limb defects
17
Q

How are the lungs formed?- week 5 and 6

A
  • During partitioning of oesophagus and respiratory diverticulum right and left lung buds form
  • Further growth and differentiation during week 5 results in formation of main bronchi from secondary bronchi (3 right, 2 left)
  • During 6th week further branches result in the formation of tertiary bronchi – these will each supply a bronchopulmonary segment (sometimes known as a bronchial tree) (10 right, 8 left)
18
Q

How are the lungs formed?- week 16, 26 and 36

A
  • Branching continues to form the terminal bronchioles by week 16 and respiratory bronchioles by week 26. First alveoli develop in week 36.
  • Branching is regulated in part by the interaction of the epithelium (derived from the foregut) with the overlying visceral mesoderm
19
Q

What does the visceral mesoderm form?

A

Visceral mesoderm forms cartilage, smooth muscle, connective tissue and capillaries – branching is regulated by the epithelium interacting with the overlying visceral mesoderm

20
Q

How is the pleura formed?

A

Lateral plate mesoderm forms the pleura
Lateral walls come together can see lateral plate mesoderm is split into two- visceral and parietal mesoderm layer- these go and form the pleuras
3D embryo- visceral mesoderm surround gut tube, parietal mesoderm forming parietal pleura

21
Q

What mesoderm forms the parietal and visceral mesoderm?

A

Visceral mesoderm forms visceral pleura, parietal mesoderm forms parietal pleura.

22
Q

What is pulmonary agenesis?

A
  • Occurs when lung bud fails to split
  • Complete absence of bronchi and vasculature
  • Can be unilateral or bilateral
  • Bilateral agenesis is incompatible with life
23
Q

What are unilateral pulmonary agenesis clinical presentations?

A
  • child usually develops respiratory distress
  • remaining lung is compromised, usually by a lower respiratory tract infection
  • 60% have other congenital anomalies including cardiac lesions, diaphragmatic hernias, and skeletal anomalies (commonly vertebral or rib anomalies)
  • Agenesis of the right lung is associated with a higher frequency of anomalies
24
Q

What is pulmonary hypoplasia?

A
  • All components are present, but incompletely developed
  • Severity of hypoplasia determines the degree of respiratory compromise
  • May be found in association with congenital diaphragmatic hernia (CDH)
25
Q

What is hypoplasia?

A

Hypoplasia= fails to form fully

26
Q

Branching morphogenesis

A

Result? supernumerary lobes or segments
Little functional significance

Branching pattern can go wrong- can have an extra lobe- R has 4 lobes- accessory lobe forms called a azygos lobe
Extra lobe doesn’t do much- little functional significance

27
Q

If diaphragm fails to form properly what happens?

A

Diaphragm- can develop an opening- intestinal contents can project into this space and form a hernia- lung can’t develop fully

28
Q

What is histogenesis of the lungs?

A

Maturation of the lungs

29
Q

Maturation of the lungs is divided into four periods- what ate they?

A
  1. Pseduoglandular
  2. Canalicular
  3. Terminal sac
  4. Alveolar
30
Q

Pseudoglandular period- 5-17 weeks- what happens?

A

Branching of the respiratory tree has occurred to form terminal bronchioles- endodermal, mesodermal signalling stimulate the branching
bronchioles but respiration not possible so foetus could not survive.

31
Q

Canalicular period -16-25 weeks- what happens?

A
  • Terminal bronchioles give rise to respiratory bronchioles, which give rise to alveolar ducts- start to develop functional area of R system
  • Mesodermal tissue becomes highly vascularised- develops more capillaries
  • Respiration is possible towards end of canalicular period as some terminal sacs have developed at the ends of the respiratory bronchioles (and remember highly vascularised)
32
Q

Terminal Sac Period- 26 – birth- what happens?

A

• Further terminal sacs (primitive alveoli- specialised air sacs) develop
• Epithelium thins and capillaries come into ‘contact’ with epithelium
• Blood-air barrier formed
-Epithelium differentiates to give rise to:
-Type I pneumocytes (across which gaseous exchange takes place)
-Type II pneumocytes which secrete surfactant

33
Q

What does surfactant do?

A
  • Surfactant forms a film over the internal walls of terminal sacs- prevents alveoli from collapsing when there is a low P
  • Decreases surface tension thus facilitating inflation

High surface tension- alveoli collapse- thus need surfactant

34
Q

Alveolar Period-36 weeks to 8 years- what happens?

A
  • Development of the lungs after birth is due mainly to an increase in the number of respiratory bronchioles and alveoli
  • 95% of mature alveoli do not develop until after birth
35
Q

What happens at birth?

A
  • Breathing movements start in utero and serve to remove amniotic fluid
  • Also kicks starts muscles of respiration into action
  • At birth any remaining lung fluid rapidly reabsorbed by capillaries
  • Baby’s first breath, air into lungs, surfactant present in sufficient amounts respiration possible
  • Circulatory changes- changes in pressure lead to this
36
Q

Respiratory distress syndrome- what is it?

A
  • If a child is born prematurely, the state of development of the lungs is usually the prime factor in determining prognosis
  • Born between 26 weeks and birth good (terminal sac and alveolar periods) chance of survival as surfactant is produced in sufficient quantities
  • Prior to this time point chances of survival poor e.g. in canalicular period
37
Q

At 23 weeks what would happen to a baby if it was born prematurely?

A
  • No surfactant produced
  • Laboured breathing (if possible) as threatens the infant with immediate asphyxiation- more effort is needed by the baby
  • Increased rate of breathing
  • Mechanical ventilation needed to support baby’s breathing
  • Damage to alveolar lining; fluid and serum proteins leak into alveolus
  • Continued injury may lead to detachment of alveolar lining
  • Chronic lung injury in preterm infants may cause bronchopulmonary dysplasia (Dysplasia means ‘abnormal formation’ so that a part/cell is abnormal )
38
Q

What are the treatments for premature babies?

A
  • Glucocorticoid treatment accelerates fetal lung development and surfactant production
  • Surfactant therapy - natural or artificial surfactant (more effective with surfactant A and B proteins)
39
Q

What is Surfactant Protein B Deficiency Disease?

A
  • Genetic condition - autosomal recessive.

* Fatal disease even with surfactant replacement therapy

Body systems- respiratory (10 decks)

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